[EXAMPLES] MessageTree should be easy to launch from an IDE

We can default to a local resource if no argument is provided.
diff --git a/examples/src/main/java/org/apache/james/mime4j/samples/tree/MessageTree.java b/examples/src/main/java/org/apache/james/mime4j/samples/tree/MessageTree.java
index 17bd138..9cd7fd2 100644
--- a/examples/src/main/java/org/apache/james/mime4j/samples/tree/MessageTree.java
+++ b/examples/src/main/java/org/apache/james/mime4j/samples/tree/MessageTree.java
@@ -362,9 +362,10 @@
     }
 
     public static void main(String[] args) {
+        final String fileName = retrieveFileName(args);
         try {
             final MessageBuilder builder = new DefaultMessageBuilder();
-            final Message message = builder.parseMessage(new FileInputStream(args[0]));
+            final Message message = builder.parseMessage(new FileInputStream(fileName));
 
             javax.swing.SwingUtilities.invokeLater(new Runnable() {
                 public void run() {
@@ -377,12 +378,19 @@
             System.err.println("Usage: org.mime4j.samples.tree.MessageTree"
                              + " path/to/message");
         } catch (FileNotFoundException e) {
-            System.err.println("The file '" + args[0] + "' could not be found.");
+            System.err.println("The file '" + fileName + "' could not be found.");
         } catch (IOException e) {
-            System.err.println("The file '" + args[0] + "' could not be read.");
+            System.err.println("The file '" + fileName + "' could not be read.");
         } catch (MimeException e) {
-            System.err.println("The file '" + args[0] + "' is invalid.");
+            System.err.println("The file '" + fileName + "' is invalid.");
         }
     }
 
+    private static String retrieveFileName(String[] args) {
+        if (args.length < 1) {
+            return ClassLoader.getSystemResource("mime-example.msg").getFile();
+        }
+        return args[0];
+    }
+
 }
diff --git a/examples/src/main/resources/mime-example.msg b/examples/src/main/resources/mime-example.msg
new file mode 100644
index 0000000..5ee0dd5
--- /dev/null
+++ b/examples/src/main/resources/mime-example.msg
@@ -0,0 +1,43 @@
+Date: Fri, 27 Apr 2007 16:08:23 +0200

+From: Foo Bar <bar@example.com>

+MIME-Version: 1.0

+To:  foo@example.com

+Subject: Here is the attachment I was waiting for.

+Content-Type: multipart/mixed;

+ boundary="------------090404080405080108000909"

+

+This is a multi-part message in MIME format.

+--------------090404080405080108000909

+Content-Type: text/plain; charset=ISO-8859-15

+Content-Transfer-Encoding: 7bit

+

+Body.

+

+--------------090404080405080108000909

+Content-Type: application/octet-stream;

+ name="data.bin"

+Content-Transfer-Encoding: base64

+Content-Disposition: attachment;

+ filename="data.bin"

+

+lLzmyQjBC2gw/hiUrcy/DDI5K6CBqFSs4NKCF67G5XBzOnSInWpZ+9Uv9IxFpz8rf871xAE+

++y0ZYES9LXDdP12svxsJ4hRsekH2HJ953Kglb3hxko7LlPlxeDX15FKH0VBE8Ggr4RbwoP+c

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+JFQcH6VA0bze/FSZoGi+sM90lyrufQngenV1EVptFBx5DQYWEWXKOi2ZS6JQGYRh1R+EXA==

+--------------090404080405080108000909--

+